The present invention relates to an assembly of a fluid coupling device and a fan, and more particularly, to an improved arrangement for attaching a fan to a fluid coupling device.
It will become apparent to those skilled in the art from the subsequent description that the mounting arrangement of the present invention may be utilized advantageously with various types of fans, as well as various types of fluid coupling devices. However, the invention is especially useful for attaching a radiator cooling fan for cooling a vehicle engine to a viscous fan drive, and the invention will be described in connection therewith. The invention is also especially useful when the fan is of the type having a hub portion and fan blades molded integrally from a plastic material, and an annular metal spider having its outer periphery attached to the hub portion and its inner periphery attached to the output coupling member of the viscous fan drive.
Because of the recent trend toward smaller automobiles, and the resultant decrease in volume of engine compartments, there has been more of a need to decrease the axial dimensions of many of the engine accessories. This need has been evident in regard to the overall axial dimension of the radiator cooling fan and viscous fan drive combination. Conventionally, fans have been rear-mounted on fan drives, but the need to reduce the axial dimension has been one factor in the trend toward front-mounting of the fan. Therefore, although the present invention may be used advantageously with either a rear-mounted or front-mounted fan, it is especially useful for a front-mounted fan and will be described in connection therewith.
Originally, almost all radiator cooling fans were assemblies of metal stampings. An attempt was made to reduce the weight and cost of cooling fans by making them from plastic moldings, but the heat generated by the viscous fan drive, when conducted to the plastic fan, frequently caused distortion of the fan, and eventual deterioration of the plastic material.
In an attempt to overcome the problem of heat transfer from the viscous fan drive to the plastic fan, those working in this art developed the fan assembly referred to previously, including the plastic hub and annular metal spider attached to the viscous fan drive. An example of such a fan assembly is illustrated in U.S. Pat. No. 3,642,382. It has become conventional practice on any type of fan having an annular metal spider for the spider to define an annular pilot surface which engages a pilot diameter on the output member of the fan drive to be sure the fan is precisely centered before bolting the spider to the fan drive. In the prior art, the pilot diameter has been disposed radially inwardly of the bolt circle, resulting in a substantial amount of surface-to-surface engagement between the spider and the fan drive.
Accordingly, it is an object of the present invention to provide an arrangement for attaching a fan assembly to a viscous fan drive which reduces the heat transfer from the fan drive to the metal spider by reducing the area of surface-to-surface engagement between the fan drive and the annular metal spider.
Efforts to increase the heat dissipation from the body (output coupling member) of the fan drive resulted in the development of a "blower body" fan drive, which is illustrated in U.S. Pat. No. 3,272,292, assigned to the assignee of the present invention. The blower body fan drive, in addition to dissipating heat from the body, draws air radially outward over the forward surface of the fan drive to minimize stagnation of air around the temperature responsive device which determines the temperatures at which the fan drive engages and disengages. It should be apparent that the standard front-mounting arrangement would interfere with the blower body front fins and the fins would, in some cases, make it more difficult to machine the pilot diameter.
Accordingly, it is another object of the present invention to provide an arrangement for attaching the annular metal spider of a combination metal-plastic fan to a fan drive of the blower body type, without seriously reducing the effective area of the front cooling fins.